Floats



De@ 24, 1963 J.' Dl-:LARUELLE ErAL 3,114,920

FLoATs Filed March 29. 1961 3 Sheets-Sheet 1 Dec. 24, 1963 J.DYELARUELLE EI'AL FLOATS 3 Sheets-Sheet 2 Filed March 129, 1961 /mw E24, 1963 J. DELARUELLE ETAL 3,114,920

FLoATs Filed March 29. 1961 3 Sheets-Sheet 3 i N l United States PatentOlitice 3,114,920 Patented Dec. 24., 1963 3,114,920 FLATS .lacquesDelaruelle and Michel Banni, Paris, France, assignors to Electricite deFrance (Service National), and Gaz de France (Service National), both atParis, France, and both French national services Filed Mar. 29, 1961,Ser. No. 99,212 Claims priority, application France Enne 2, 1960 Ciaims.(Cl. 9 3) This invention relates to floats, and in particular to oatsintended for holding submarine cables and pipelines (hereinafterreferred to as submarine tubes for simplicity) according to thetechniques described in the speciiication of French Patent No. 1,206,378of the 14th of August 1958, and the specification of a French patentapplication of the 4th of August 1959, led as an application for apatent of addition to French Patent No. 1,205,- 378, as well as in thespecilication of our co-pending patent application No. 99,148 filedMarch 29, 1961.

This invention concerns iloats of the type comprising a buoyancy masswhich is uid and compressible, and an object of the invention is toprovide means permitting the utilisation of variations of the Volume ofthis type of buoyancy mass as a function of the depth of immersion ofthe float. For floats in which the buoyancy mass is liquid, it is asubsidiary object of the invention to avoid crushing of the envelope dueto the inevitable compressibility of the liquid.

A more particular object of the invention consists in the provision of afloat having a buoyancy which is variable with the depth of immersionfor use in one of the techniques described in the specification of ourabovementioned co-pending patent application.

According to the invention there is provided a buoyancy oat, comprisinga rigid envelope, and a flexible envelope formed from an impermeablematerial surrounded by the rigid envelope, the envelopes dening twochambers, the first of which contains a buoyancy mass comprising anelastic fluid under a pressure equal to the hydrostatic pressurecorresponding to a predetermined immersion depth, and the second ofwhich is in communication with the outside of the oat to permit entry ofthe surrounding liquid into the second chamber when the oat is immersed.

With this arrangement, any variation of the volume of the buoyancy massis automatically compensated by an inverse variation of the volume ofthe surrounding liquid: the system is maintained under balanced pressureand any direct contact is avoided between the surrounding liquid (ingeneral sea Water) and the buoyancy mass.

A buoyancy float, the buoyancy of which decreases when the loat isimmersed beyond a given depth, may employ a gaseous buoyancy masscharged under a pressure of inflation corresponding to the hydrostaticpressure at the selected depth.

Alternatively, a buoyancy tioat, the buoyancy or which varies slowlywhen the lloat is immersed may employ a liquid buoyancy mass.

In order to enable the invention to be more readily understood,reference will now be made to the accompanying drawings, whichillustrate diagrammatically and by way of example two embodimentsthereof, and in which:

FIGURE l is an elevational View of a spherical loat containing acompressed gas;

FIGURE 2 is a sectional view, on a larger scale, showing a detail of thefloat shown in FIGURE 1, and

FIGURE 3 is an elevational view of a cylindrical float containing aliquid charge.

Referring now to FIGURES 1 and 2, there is shown a buoyancy iloat forsubmarine tubes, the oat being constituted by a hollow metallic sphere 1of welded steel, of which the diameter and thickness will be chosen inaccordance with the conditions under which the float will be used. Ashort radial neck 2 is welded to the sphere 1 and carries at one end acircular opening 3 and at the other end a collar d, the neck beingbraced by four gussets or vanes 5 placed at 90 to one another. Twodiametrically opposed vanes are each formed with a hole 6 capable ofreceiving a ring.

The neck 2 is closed by a solid plate 7 formed with bolt holesregistering with bolt holes in the collar 4, and the plate 7 carries atits centre a respiration tube 8. One end of the tube 3 protrudes beyondthe plate 7 and is provided with a strainer 9 whilst the internal partof the tube 8 in the region situated in the interior of the neck 2comprises a channelled surface 1d. The remainder of the tube extendsradially into the sphere and is formed with numerous small holes 11, thetube termimating in a rounded end.

The diameter of the neck 2 is suiiicient to allow the introduction of abladder 13 of impermeable fabric having a reinforced nozzle 14 adaptedto be engaged on the cbannelled part of the respiration tube 8 and to befixed and sealed there by a series of screw-clamps 15. If desired, thenozzle 1d may be bonded on to the channelled surface lll. In an inflatedstate, the bladder 13 constitutes a spherical balloon with a diameterslightly greater than the internal diameter of the sphere. A mouthpiece16, equipped with a compressed air valve 17, is Welded on the neck 2,and at the lower part of the sphere opposite the opening 3, a bracket18, which is welded on a plate 1.9, supports a ring 2d of cast-iron onwhich a support cable for the submarine tube can be fastened. A drain 21blocked by a solid bush is welded as close as possible to the plate 19.

In the use of the oat, the sphere is fitted with the bladder 13 and theplate 7 is carefully bolted down on to the collar 4 so as to ensure aperfectly sealed closure. The oat is then inflated by connecting themouthpiece 16 to a source of compressed air at a predetermined pressure.The pressure of air causes the bladder 13 to wrap itself closely aroundthe respiration tube 8.

In the course of the progressive immersion of the float, water flows inthrough the strainer 9 into the respiration tube 3, but first remainsconned in the interior or the latter. When, however, the hydrostaticpressure ot the ambient medium exceeds tbe inilation pressure, the waterwill escape through the holes 11 of the respiration tube to the interiorof the bladder i3 and increase the volume of the latter at the expenseof the volume of the air which is compressed according to Mariottes law,so that the buoyancy of the float decreases to become nil and iinallynegative, the procedure being reversed and the buoyancy increasing asthe iioat is raised.

S0 that the float always has a positive buoyancy, there is linked to ita second iloat (not shown) of polystyrene, for example, adapted tocompensate the weight in the water of the metallic part of the float andits accessories.

A certain number of the oats just described may be hooked at regularintervals along an immersed tube, so that if v is the volume of floatadded per linear metre of the tube, and h1 is the hydrostatic pressure(in metres of water) corresponding to the ination pressure, thecorresponding buoyancy will remain equal to v whilst the depth ofimmersion h is less than h1, neglecting the weight of the air introducedunder pressure and by assuming that the density of the liquid is equalto one.

For a depth z greater than h1, the buoyancy becomes:

The buoyancy exerted .by the a seinbly of floats 0n an immersed tube upto a depth H thus becomes:

The weight of the tube being equal to pH (Where p is the apparent weightper linear metre of the immersed tube), the tube is in equilibrium ifpH-fF and descends if pH F.

It will thus be seen that it is possible to control the equilibrium orto unbalance it by varying the v, and thus by varying the volume and thespacing of the fioats and the inflation pressure h1.

The impermeable membrane prevents the dissolution of the air in thewater, which dissolution would occur at elevated pressure. Furthermore,the use of valves is completely avoided, which is an advantage since thefunctioning of valves can be subject to failures.

In place of the oat which has just been described with reference toFIGURES l and 2 Where the water can be present at the centre of thecontainer, it is possible to provide an inverse type of iloat with theair at the centre of the container. ln this case, the principle of aninilated spherical balloon which collapses when it is in a medium ofwhich the pressure is greater than its inflation pressure is employed,and the inilated balloon may be placed inside a metallic sphere formedwith holes. As in the case of the respiration tube S of FIGURES l and 2,these holes must have a suiciently small diameter in order to avoid theelfects of pricking. It is furthermore possible to replace or to doublethe sheet sphere by one or several layers of grids, one of which is veryline in order to avoid the efect of prickinv.

In the case of oats using a charge of a liquid having a low density suchas light petrol, butane, propane, cylindrical envelopes which could beeither eilexible or rigid are preferred. In all cases thecomprcssibility of the liquids, the variation of their density as afunction of temperature, and the vapour pressure which necessitates themaintenance in the interior of the envelope of a dead space containingthe vapour and which is cornpressed a substantial amount with theincrease of pressure must be taken into account. These di'erentproperties act in the same direction and lead to a reduction of thevolume with increase of depth, which is much more important when thedensity is low.

In the case of flexible envelope oats constituted for example of acylinder of rubberised sheet or of plastic, where the contents areconstantly in pressure equilibrium with the surrounding sea Water, theenvelope only undergoes a compression force perpendicular to itssurface. Taking account of the strength of cloths available, thediameter of the cylindrical reservoir constituting the tloat is in factlimited by the necessity of resisting the vapour pressure of the liquid.This type of oat can in practice only be used for light petrol, the useof butane and particularly of propane leading to reservoir diameterswhich are much too small.

Floats with regid envelopes are not subject to these limitations and thecontraction of the volume of their liquid charge will be compensated,without subjecting the rigid envelope to compression forces by thenitroduction of sea water under the pressure of the ambient medium asdescribed with reference to FIGURES l and 2.

FIGURE 3 shows a float having rigid cylindrical envelope for a liquidcharge. A reservoir 3l. of general cylindrical form is formed from atube of steel with caps 32 and 33 welded on to it. The end cap 32carries a neck 311iwith a collar 35 closed by a plate 36 carrying, in amanner similar to that which has been described with reference toFIGURES 1 and 2, a respiration tube 3S which is terminated outside theplate 36 by a screen 39 and which is surrounded inside the reservoir 3lby a cylinder' db of impermeable material ciosed at one end andterminated at .theother end by a nozzle l fixed and bonded on achannelled and non-perforated part of the tube The metallic reservoir 3lcomprises on its upper surface a device 42 for filling and evacuatingthe reservoir with the liquid fbutane or propane) and for controlling ofthe liquid level, the device d?, also acting as a safety device. On thelower surface of the reservoir, two or more rings '53 and are supportedand serve for the passage of the cables for the support of the submarinetube. Another ring 45 is provided on the cnd can 33 for towing thelloat.

lli/hen the reservoir is lled with the liquid, the cylinder iti iscompletely Hatten-ed by the pressure of the liquid and its vapourpressure. As the float is immersed, the contraction of the liquid iscompensated by the progressive entry into the cylinnder 4G of sea waterwhich can never come into contact with the filling liquid. The system isthus maintained in itself under equal pressure. When the oat is raised,the process is reversed, and the water is progressively driven from thecylinder It will thus be seen that in this case a slov.r and continuousreduction of the buoyancy is obtained as soon as the lloat is immersed.However, by arranging in the floats shown in FIGURE 3 an appropriateevacuated space above the level of the liquid and by filling this spacewith a gas at a pressure higher than the vapour pressure of the liquid,a mixed iloat can be produced in the sense that the iloat then functionsin part as a liquid oat (as shown in FIGURE 3) and in part as a gasfloat (as shown in FIGURES l and 2). However, in practice, it isgcnerally preferable to separate the two types of iloat.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

l. An automatically variable buoyancy float, comprising a rigidenvelope, and a flexible envelope formed from an impermeable materialsurrounded by the rigid envelope, the envelopes defining two chambers,one of the chambers being the rigid envelope which contains andpermanently confines a buoyancy mass comprising an elastic fluid under apressure equal to the hydrostatic pressure corresponding to apredetermined immersion depth, `and the second of the chambers being theilexible envelope which is in permanent communication with the outsideof the float to permit entry of the surrounding liquid into the secondchamber when the float is immersed beyond the said predetermined depth.

2. The float of claim l, wherein thc buoyancy mass is a gas.

3. The iioat of claim l, wherein the buoyancy mass is a liquid.

4. rl`he iloat of claim l, wherein the buoyancy mass is a composite masscomprising a liquid mass surmountcd by a mass of gas compressed to thepredetermined pressure.

5. An automatically variable buoyancy float, comprising a rigid envelopedefining a first chamber, a neck member on said envelope, a ilexibleimpermeable envelope defining a second chamber, a neck member on saidIlexible envelope, a cover for the neck member on the rigid envelope,means securing said cover to said neck member on the rigid envelope, atube passing through said cover and said neck member into the interiorof the rigid envelope, means securing the neck member of said flexibleenvelope around said tube, and within the neck member of the rigidenvelope, means establishing permanent communication between theinterior of said ilexible cnvelope and the exterior of the float throughthe intermediary of said tube, and means on said neck member of saidrigid envelope for introducing into said first cbamber and permanentlyconfining therein a buoyancy mass at a pressure equal to the hydrostaticpressure corresponding to a predetermined immersion depth.

6. The iloat of claim 5, wherein said means for establishing saidcommunication includes an apertured screen 10. The iloat of claim 5,wherein both said envelopes carried on the end of the tube exterior ofthe oat, and are substantially cylindrical. a perforated portion of saidtube within said flexible en- Vope. References Cited in the tile of thispatent The iloat of claim 5, Wherem the buoyancy mass 1s 5 UNITED STATESPATENTS 8. The oat of claim 5, wherein the buoyancy mass 576,052 GrantJan. 26, 1897 is a liquid which is substantially lighter than Water.952,452 Leon Mar. 22, 1910 9. The loat of claim 5, wherein the rigidenvelope is 2,371,404 Mumford Mar. 13, 1945 spherical.

1. AN AUTOMATICALLY VARIABLE BUOYANCY FLOAT, COMPRISING A RIGIDENVELOPE, AND A FLEXIBLE ENVELOPE FORMED FROM AN IMPERMEABLE MATERIALSURROUNDED BY THE RIGID ENVELOPE, THE ENVELOPES DEFINING TWO CHAMBERS,ONE OF THE CHAMBERS BEING THE RIGID ENVELOPE WHICH CONTAINS ANDPERMANENTLY CONFINES A BUOYANCY MASS COMPRISING AN ELASTIC FLUID UNDER APRESSURE EQUAL TO THE HYDROSTATIC PRESSURE CORRESPONDING TO APREDETERMINED IMMERSION DEPTH, AND THE SECOND OF THE CHAMBERS BEING THEFLEXIBLE ENVELOPE WHICH IS IN PERMANENT COMMUNICATION WITH THE OUTSIDEOF THE FLOAT TO PERMIT ENTRY OF THE SURROUNDING LIQUID INTO THE SECONDCHAMBER WHEN THE FLOAT IS IMMERSED BEYOND THE SAID PREDETERMINED DEPTH.